**7. Challenges and opportunities for the use of biopesticides**

Over-reliance on chemical control results in changes in the status of cotton pests and environmental pollution [7]. There are still challenges to sustain the environment for cotton production [128]. Much research has focused on advancing pest control, and biological control agents are an important criterion for sustainable agriculture [129, 130]. Biopesticides or biological pesticides are an eco-friendly alternative to chemical pesticides [131]. They can play a significant role in the integrated pest management of many insect pests [132]. They are obtained from the environment to control agricultural diseases and insects [15]. They are only about 5% of the total crop protection market; however, they are expected to surpass synthetic pesticides by 2050 [133]. The production of biopesticides is sometimes highly labour intensive and difficult to produce at levels that are economically viable and profitable [134]. Enhancement of biopesticides has been explored by improving different compounds to sustain their efficacy as well as the shelf life [135, 136]. The development of non-toxic and effective biopesticides requires a holistic approach, which will turn most of the research results into profitable business products. Although this section provides generalities, each biopesticide needs to be individually assessed to determine its impacts on pest control, humans, the environment, and other factors associated with the adoption by farmers. The adoption of biopesticides by farmers relies on their efficacy, increased yield, lower prices, and an efficient supply [137]. They have been unreliable and very costly due to their limited market share [138]. However, Sharma et al. [107] reported that bacterial biopesticides are the most widely used and less expensive than other control measures. Biopesticides benefit the farmers due to target specificity, the ability to manage the pest rather than eradicate, and conservation of environmental *Role of Microbial Biopesticides as an Alternative to Insecticides in Integrated Pest Management… DOI: http://dx.doi.org/10.5772/intechopen.100400*

balance [131]. The very high specificity of the products might be a disadvantage when a complex pest species needs to be controlled. Baculovirus-based insecticides have been considered safe on non-target organisms and can be used as part of integrated pest management to ease the risks of synthetic insecticides [99]. However, baculoviruses are reported to act slowly in killing the targeted pests [60], which has led to the development of faster killing products through genetic modifications [94, 102]. Baculoviruses are also reported to be less effective due to their high susceptibility to ultraviolet radiation, and this requires the reapplication of the virus over time [139, 140]. This effectively increases input costs that farmers may incur. The activity of nucleopolyhedrovirus has been found to decrease significantly over time after applying the virus on the plant leaves [116]. When exposed to direct sunlight, nucleopolyhedrovirus has been reported to be inactivated within a day or two [141]. *B. thuringiensis* has a vast spectrum of insecticidal activity compared to other bacteria, and it is safe for the environment and humans [142]. *B. thuringiensis* does not affect non-target organisms, except for some closely related insects to the target pests [143]. The application of *B. thuringiensis* as a biopesticide is potent and biodegradable than synthetic insecticides [144]. However, the bacterium is effective when the present part of the plant that the target insect feeds on and when larvae are still early instars [144].

The efficiency of entomopathogens mainly relies on their ability to infect the target insect and their persistence [145]. Microbial insecticides have low persistence in the environment, and they require accurate application because many of these pathogens are insect-specific [33]. Namasivayam and Vidyasankar [130] recorded that various formulations of *M. rileyi* are persistent under different temperatures. They further recommended that using bio gel formulation of *M. rileyi* might play a role in controlling pests under field conditions. However, Edelstein et al. [146] reported that this pathogen is extremely sensitive to nutritional and environmental conditions, affecting the virulence of the asexual reproductive spore of fungi and stability in storage [147]. Further research is required to stabilize *M. rileyi* in storage and determine the insecticidal activity of formulated conidia [148]. The persistence of *B. bassiana* under field conditions is negatively affected due to ultraviolet light, extreme temperatures and rain [58]. Sandhu et al. [149] have reported that this pathogen can live longer at lower temperatures and relative humidity. Bouslama et al. [150] demonstrated that some formulations of *B. thuringiensis* could be persistent after rain wash compared to treatment with an unformulated bacterium. Biopesticides that degrade rapidly in the environment may have a short field persistence resulting in numerous product applications [60]. The major constraints of biopesticides are limited to, among others, environmental conditions such as solar ultraviolet radiation, temperature, humidity and their ability on spreading on the surface [145, 151]. Since biopesticides often contain living material, the products have reduced shelf life. Temperature, moisture or humidity also plays a role in the shelf life of the biopesticides [152]. Due to their practical limitations, such as rapidly washing away in rain and degradation by the sunlight, biopesticides may not be as effective as synthetic pesticides. The impact of rain on the persistence of entomopathogenic fungi is less when the conidia are in direct contact with the cuticle of leaves and larvae [153]. Under natural conditions, biopesticides often cause natural mortalities of insect populations [149]. Inglis et al. [154] noted that the influence of rain has a minimal effect on *B. bassiana* persistence; however, high rains washed away significant quantities of *B. bassiana* from leaves. *B. thuringiensis* is reported to persist for few days after application due to weather, UV light, chemical environment and the presence of proteinases [144]. Like the other biopesticides, most spores are washed off into the soil.
